As bicycles increasingly become a popular form of recreation, exercise, as well as transportation, manufacturers and riders have sought to make bicycles that are more light-weight and versatile. Many bicycles have been designed to have a multi-speed function so that a rider can selectively vary the gear-ratio (also known as “speed-changing”) between the driving (e.g., front) sprocket and the driven (e.g., rear) sprocket according to different road conditions. Speed-changing enables the rider to use a lower gear (e.g., with a sprocket with a lower teeth count) to generate greater low-end torque and easier start, and a higher gear (e.g., with a sprocket with a higher teeth count) to generate faster high-end speed. Typically, a gear-changing apparatus, for example, a well-known bicycle derailleur such as disclosed in the U.S. Pat. No. 4,259,873 to Nagano, is employed on the bicycle to shift a driving chain between a larger sprocket and a smaller sprocket in order to “change the speed.” However, the gear-changing apparatus often involves push-pull control wires, control levers, springs, chain-guide pulleys, and/or other movable mechanical parts that are complex, heavy, and subject to wear and tear.
Indeed, in the realm of competitive cycling, reducing the possibility of mechanical failure and reducing the weight of a bicycle can provide the rider with great competitive advantages, and they often take priority over having the benefit of speed-changing because of those drawbacks associated with gear-changing apparatus mentioned above. For example, in track cycling where bicycles are raced on specially built banked tracks, or in BMX competitions where bicycles are ridden in a harsh or off-road environment, the riders often opt for single-speed bicycles over multi-speed bicycles because of the possible mechanical failures, extra weight, and/or cost involved with conventional speed-changing mechanisms. As such, to get the best the overall performance, compromising decisions have to be made in selecting a single gear-ratio in hope that the selected gear-ratio would sacrifice neither too much low-end torque nor too much top-end speed.
Thus, it would be highly desirable to provide a bicycle sprocket that retains multi-speed functionality with a minimum number of moving parts while still being durable, light-weight, and easy to manufacture.
Like reference numerals refer to corresponding parts throughout the drawing figures.